Method of manufacturing III-nitride crystal

ABSTRACT

Provided is a method of manufacturing III-nitride crystal having a major surface of plane orientation other than {0001}, designated by choice, the III-nitride crystal manufacturing method including: a step of slicing III-nitride bulk crystal through a plurality of planes defining a predetermined slice thickness in the direction of the designated plane orientation, to produce a plurality of III-nitride crystal substrates having a major surface of the designated plane orientation; a step of disposing the substrates adjoining each other sideways in a manner such that the major surfaces of the substrates parallel each other and such that any difference in slice thickness between two adjoining III-nitride crystal substrates is not greater than 0.1 mm; and a step of growing III-nitride crystal onto the major surfaces of the substrates.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention, involving Group-III nitride crystal manufacturingmethods, relates to a method of manufacturing III-nitride crystal havinga major surface of plane orientation other than {0001}, designated bychoice, and to semiconductor devices utilizing the crystal.

2. Description of the Related Art

Group-III nitride crystals, which are employed advantageously insemiconductor electronic devices including light-emitting devices andsemiconductor sensors, are ordinarily manufactured by growing crystalonto the major surface of a sapphire substrate having a (0001) planemajor surface, or onto a GaAs substrate having a (111) A-plane majorsurface, by means of a vapor-phase technique such as hydride vapor-phaseepitaxy (HVPE) or metalorganic chemical vapor deposition (MOCVD), or byflux growth or other liquid-phase technique. Consequently, ordinarilyobtained III-nitride crystals have a major surface whose planeorientation is {0001}.

With light-emitting devices on substrates that are III-nitride crystalhaving a major surface whose plane orientation is {0001}, and in which amultiquantum-well (MQW) structure as a light-emitting layer has beendeposited on the major surface, the light-emission efficiency isdecreased by spontaneous polarization that occurs within thelight-emitting layer owing to the III-nitride crystal's <0001> orientedpolarity. Consequently, the manufacture of III-nitride crystal having amajor surface whose plane orientation is other than {0001} is beingsought.

Reference is made, for example, to Japanese Unexamined Pat. App. Pub.No. 2005-162526: The following method has been proposed as way ofpreparing gallium-nitride crystal having a surface plane orientation ofchoice, without influencing the plane orientation of the major surfaceof the substrate. Namely, according to the method disclosed in Pat. App.Pub. No. 2005-162526, a number of rectangular crystal masses are dicedfrom GaN crystal grown by vapor deposition. Meanwhile, a silicon oxidefilm is coated onto the surface of a separately readied sapphiresubstrate, and subsequently a number of recesses reaching to thesubstrate are formed in the film. Next, the numerous crystal masses areembedded into the recesses in a manner such that their top surfaces willhave the same plane orientation. Then, by vapor deposition with thecrystal masses as seeds, gallium nitride crystal having a surface planeorientation of choice is grown.

BRIEF SUMMARY OF THE INVENTION

With the method in Pat. App. Pub. No. 2005-162526, however, inasmuch asgrowth of the GaN crystal is carried out with, as seeds, the masses ofcrystal GaN that have been embedded into the sapphire substrate, due tothe disparity in thermal expansion coefficient between sapphire and GaN,fractures and strains appear in the GaN crystal when the crystal iscooled following the growth process, such that GaN crystal of superiorcrystallinity has not been obtainable.

Furthermore, if III-nitride crystal containing Al—for example,Al_(x)Ga_(y)In_(1-x-y)N (x>0, y≧0, x+y≦1)—is grown by the method in Pat.App. Pub. No. 2005-162526, because the Al precursor is not selectivewith respect to the silicon oxide film, the Al_(x)Ga_(y)In_(1-x-y)Ngrows onto the silicon oxide film as well, and consequentlyAl_(x)Ga_(y)In_(1-x-y)N crystal of superior crystallinity has not beenobtainable.

An object of the present invention, to resolve the problems discussedabove, is to make available a method of manufacturing III-nitridecrystal of superior crystallinity, having a major surface of planeorientation other than {0001}, designated by choice, and to makeavailable semiconductor devices, utilizing III-nitride crystal obtainedby the manufacturing method, that excel in light-emission efficiency.

In accordance with an embodiment of the present invention, provided is amethod of manufacturing III-nitride crystal having a major surface ofplane orientation other than {0001}, designated by choice, theIII-nitride crystal manufacturing method including: a step of slicingIII-nitride bulk crystal through a plurality of planes defining apredetermined slice thickness in the direction of the designated planeorientation, to produce a plurality of III-nitride crystal substrateshaving a major surface of the designated plane orientation; a step ofdisposing the substrates adjoining each other sideways in a manner suchthat the major surfaces of the substrates parallel each other and suchthat any difference in slice thickness between two adjoining III-nitridecrystal substrates is not greater than 0.1 mm; and a step of growingIII-nitride crystal onto the major surfaces of the substrates.

In accordance with another embodiment of the present invention, thedesignated plane orientation is misoriented by an off angle of 5° orless with respect to any crystallographically equivalent planeorientation selected from the group consisting of {1-10x} (wherein x isa whole number), {11-2y} (wherein y is a whole number), and {hk-(h+k)l}(wherein h, k and l are whole numbers).

In accordance with another embodiment of the present invention, thedesignated plane orientation is misoriented by an off angle of 5° orless with respect to {1-100} plane orientations.

In accordance with another embodiment of the present invention, thedesignated plane orientation is misoriented by an off angle of 5° orless with respect to any crystallographically equivalent planeorientation selected from the group consisting of {11-20}, {1-10±2},{11-2±2}, {20-2±1} and {22-4±1}.

In accordance with another embodiment of the present invention, theroughness average Ra of the faces along which the substrates adjoin eachother is 50 nm or less.

In accordance with another embodiment of the present invention, providedis the method further comprising a step of grinding/polishing theplurality of III-nitride crystal substrates such that the surfaceroughness of the substrate major surfaces is not greater than 50 nm.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A, a schematic diagram for illustrating one mode of embodying aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 1B, a schematic diagram for illustrating one mode of embodying aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 1C, a schematic diagram for illustrating one mode of embodying aIII-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 2A, a diagram summarily illustrating an undersubstrate for growingbulk III-nitride crystal, represents a schematic plan view.

FIG. 2B, a diagram summarily illustrating an undersubstrate for growingbulk III-nitride crystal, represents a schematic sectional view alongIIB-IIB in FIG. 2A.

FIG. 3A, a schematic diagram for illustrating one example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 3B, a schematic diagram for illustrating one example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 3C, a schematic diagram for illustrating one example of aIII-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 4 is a sectional view summarily representing a crystal-growthprocess step in another example of a III-nitride crystal manufacturingmethod involving the present invention.

FIG. 5A, a schematic diagram for illustrating still another example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 5B, a schematic diagram for illustrating the still other example ofa III-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 5C, a schematic diagram for illustrating the still other example ofa III-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 6A, a schematic diagram for illustrating yet another example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 6B, a schematic diagram for illustrating the yet other example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 6C, a schematic diagram for illustrating the yet other example of aIII-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 6D, a schematic diagram for illustrating yet another example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 6E, a schematic diagram for illustrating the yet other example of aIII-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 7A, a schematic diagram for illustrating a further example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 7B, a schematic diagram for illustrating the further example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 7C, a schematic diagram for illustrating the further example of aIII-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 7D, a schematic diagram for illustrating the further example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 7E, a schematic diagram for illustrating the further example of aIII-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 8A, a schematic diagram for illustrating a still further example ofa III-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 8B, a schematic diagram for illustrating the still further exampleof a III-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 8C, a schematic diagram for illustrating the still further exampleof a III-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 9A, a schematic diagram for illustrating a yet further example of aIII-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 9B, a schematic diagram for illustrating the yet further example ofa III-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 9C, a schematic diagram for illustrating the yet further example ofa III-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 10A, a schematic diagram for illustrating an even further exampleof a III-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of slicing off substrates.

FIG. 10B, a schematic diagram for illustrating the even further exampleof a III-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 10C, a schematic diagram for illustrating the even further exampleof a III-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 10D, a schematic diagram for illustrating the even further exampleof a III-nitride crystal manufacturing method involving the presentinvention, is an oblique perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 10E, a schematic diagram for illustrating the even further exampleof a III-nitride crystal manufacturing method involving the presentinvention, is a sectional view summarily representing a crystal-growthprocess step.

FIG. 11A, a schematic diagram for illustrating a yet even furtherexample of a III-nitride crystal manufacturing method involving thepresent invention, is an oblique perspective view summarily representinga process step of slicing off substrates.

FIG. 11B, a schematic diagram for illustrating the yet even furtherexample of a III-nitride crystal manufacturing method involving thepresent invention, is an oblique perspective view summarily representinga process step of arranging substrates into a row.

FIG. 11C, a schematic diagram for illustrating the yet even furtherexample of a III-nitride crystal manufacturing method involving thepresent invention, is a sectional view summarily representing acrystal-growth process step.

FIG. 11D, an schematic diagram for illustrating the yet even furtherexample of a III-nitride crystal manufacturing method involving thepresent invention, is an perspective view summarily representing aprocess step of arranging substrates into a row.

FIG. 11E, a schematic diagram for illustrating the yet even furtherexample of a III-nitride crystal manufacturing method involving thepresent invention, is a sectional view summarily representing acrystal-growth process step.

FIG. 12 is a schematic sectional diagram of a light-emitting devicemanufactured utilizing epitaxial III-nitride crystal involving thepresent invention.

FIG. 13 is a schematic sectional diagram of a light-emitting devicemanufactured utilizing epitaxial III-nitride crystal involving thepresent invention.

FIG. 14 is a schematic sectional diagram of an electronic devicemanufactured utilizing epitaxial III-nitride crystal involving thepresent invention.

FIG. 15 is an oblique perspective view diagram summarily representing aconcrete example of {1-10x} (x: a whole number) planes in a unit cell ofa III-nitride crystal that is hexagonal.

FIG. 16 is an oblique perspective view diagram summarily representing aconcrete example of {11-2y} (y: a whole number) planes in a unit cell ofa III-nitride crystal that is hexagonal.

FIG. 17 is an oblique perspective view diagram summarily representing aconcrete example of {hk-(h+k)l} (h, k and l: whole numbers) planes in aunit cell of a III-nitride crystal that is hexagonal.

LEGEND

1: III-nitride bulk crystal

10 p, 10 q: III-nitride crystal substrates

10 pm, 10 qm, 20 m: major surfaces

10 pt, 10 qt: adjoining faces

20: III-nitride crystal

20 f: facet

20 s: direct-over-substrate region

20 t: adjoining-substrate supra-region

20 v: pit

21: III-nitride wafer

90: undersubstrate

91: mask

91 w: window

DETAILED DESCRIPTION OF THE INVENTION

In crystallography, in order to represent the plane orientation ofcrystal faces, notation (Miller notation) such as (hkl) and (hkil) isused. The plane orientation of crystal faces in crystals of thehexagonal crystal system, such as III-nitride crystal, is expressed by(hkil). Herein, h, k, i and l are whole numbers referred to as Millerindices, where the relationship i=−(h+k) holds. The plane of the planeorientation (hkil) is called the (hkil) plane. And the directionperpendicular to the (hkil) plane (the direction of a line normal to the(hkil) plane) is called the [hkil] direction. Meanwhile, “{hkil}”generically signifies plane orientations comprehending (hkil) as well aseach of its crystallographically equivalent orientations, and “<hkil>”generically signifies directions comprehending [hkil] as well as each ofits crystallographically equivalent directions.

One mode of embodying a III-nitride crystal manufacturing methodinvolving the present invention is a method, with reference to FIG. 1,of manufacturing a III-nitride crystal 20 having a major surface 20 m ofplane orientation {h₀k₀i₀l₀} other than {0001}, designated by choice,and includes the following steps. The first step is, as indicated inFIG. 1A, a step of slicing (which will also be termed a “slice-offsubstrates step” hereinafter) III-nitride bulk crystal 1 into aplurality of III-nitride crystal substrates 10 p, 10 q having {h₀k₀i₀l₀}major surfaces 10 pm, 10 qm. The second step is, as indicated in FIG.1B, a step of disposing (which will also be termed a “substrateplacement step” hereinafter) the substrates 10 p, 10 q adjoining eachother sideways in such a way that the major surfaces 10 pm, 10 qm of theplurality of III-nitride crystal substrates 10 p, 10 q parallel eachother and so that the [0001] directions in the substrates 10 p, 10 q areoriented in the same way. The third step is, as indicated in FIG. 1C, astep of growing (which will also be termed a “crystal growth step”hereinafter) III-nitride crystal 20 onto the major surfaces 10 pm, 10 qmof the plurality of III-nitride crystal substrates 10 p, 10 q.

In the first step (the slice-off substrates step) in the presentembodying mode, a plurality of III-nitride crystal substrates 10 p, 10 qhaving {h₀k₀i₀l₀} major surfaces 10 pm, 10 qm is sliced from III-nitridebulk crystal 1.

The III-nitride bulk crystal 1 utilized in this first step is notparticularly limited; crystal manufactured by ordinary methods—that is,growing crystal by HVPE, MOCVD, or other vapor deposition technique, orby flux growth or other liquid-phase technique, onto the major surfaceof, for example, a sapphire substrate having a (0001) major surface or aGaAs substrate having a (111) A-plane major surface—is adequate.Accordingly, although the III-nitride bulk crystal is not particularlylimited, ordinarily it has a {0001} major surface. Here, from theperspective of diminishing dislocation density and enhancingcrystallinity, it is preferable that the III-nitride bulk crystal 1 begrown, as is disclosed in Japanese Unexamined Pat. App. Pub. No.2001-102307, by a facet growth technique characterized in that facetsare formed on the surface where the crystal grows (the crystal growthface), and crystal growth is carried out without filling in the facets.

Likewise, there are no particular limitations on the method whereby theplurality of III-nitride crystal substrates 10 p, 10 q having {h₀k₀i₀l₀}major surfaces 10 pm, 10 qm is sliced from the III-nitride bulk crystal1; as indicated in FIG. 1A, the III-nitride bulk crystal 1 can be cutthrough a plurality of planes having a predetermined perpendicularspacing along an <hkil> direction (the plane orientation of these planesbeing {hkil}, they are also referred to as {hkil} planes, as they willbe hereinafter).

In the second step (the substrate placement step) in the presentembodying mode, as indicated in FIG. 1B, the plural sliced-offIII-nitride crystal substrates 10 p, 10 q are disposed adjoining eachother sideways in a manner such that the major surfaces 10 pm, 10 qm ofthe substrates 10 p, 10 q parallel each other and such that the [0001]directions in the substrates 10 p, 10 q are oriented in the same way. Inthis case, while two adjoining III-nitride crystal substrates 10 p, 10 qamong the plurality of III-nitride crystal substrates have been labeledwith reference marks in FIG. 1B, the situation is the same with theother adjoining III-nitride crystal substrates.

The plural III-nitride crystal substrates 10 p, 10 q are disposedsideways so that the major surfaces 10 pm, 10 qm of the substrates 10 p,10 q parallel each other, because if the angles formed by the majorsurfaces of the substrates and their crystal axes are not uniform alongthe substrates' major surface, the chemical composition of theIII-nitride crystal grown onto the major surfaces of the substrates willbe non-uniform along a plane parallel to the substrates' major surface.It is sufficient that the major surfaces 10 pm, 10 qm of the substrates10 p, 10 q be parallel to each other; they need not necessarily be flushwith each other. Nevertheless, the difference in height ΔT between themajor surfaces 10 pm, 10 qm of two adjoining III-nitride crystalsubstrates 10 p, 10 q is preferably 0.1 mm or less, more preferably 0.01mm or less.

Furthermore, from the perspective of designing for more uniform crystalgrowth by making the crystal orientations of the plural III-nitridecrystal substrates 10 p, 10 q the same, the substrates 10 p, 10 q aredisposed sideways in a manner such that the [0001] directions of thesubstrates 10 p, 10 q are oriented in the same way. And the pluralIII-nitride crystal substrates 10 p, 10 q are disposed adjoining eachother because if there are gaps between substrates, the crystallinity ofcrystal that grows over the gaps would be compromised.

Reference is made to FIGS. 1A and 1B: By the first step (the slice-offsubstrates step) and the second step (the substrate placement step),from III-nitride bulk crystal 1 a plurality of III-nitride crystalsubstrates 10 p, 10 q having {h₀k₀i₀l₀} major surfaces 10 pm, 10qm—disposed side-by-side in a manner such that the major surfaces 10 pm,10 qm of the plurality of III-nitride crystal substrates 10 p, 10 q areparallel to each other and the [0001] directions in the substrates 10 p,10 q are oriented in the same way—is obtained.

In the third step (crystal growth step) in the present embodying mode,III-nitride crystal 20 is grown onto the major surfaces 10 pm, 10 qm ofthe plurality of III-nitride crystal substrates 10 p, 10 q. In thiscase, growth of the III-nitride crystal 20 is epitaxial growth. Inasmuchas the major surfaces 10 pm, 10 qm of the plurality of III-nitridecrystal substrates 10 p, 10 q have {h₀k₀i₀l₀} plane orientation, themajor surface 20 m of the III-nitride crystal 20 epitaxially grown ontothe major surfaces 10 pm, 10 qm has the same plane orientation{h₀k₀i₀l₀} as the major surfaces 10 pm, 10 qm of the plurality ofIII-nitride crystal substrates 10 p, 10 q. Again, inasmuch asIII-nitride crystal 20 is grown onto the major surfaces 10 pm, 10 qm ofthe plurality of III-nitride crystal substrates 10 p, 10 q, thedifference in thermal expansion coefficient between the substrates 10 p,10 q and the III-nitride crystal 20 that is grown is slight, thanks towhich fractures and strains are unlikely to appear in the grown crystalduring post-crystal-growth cooling, yielding III-nitride crystal ofsuperior crystallinity. From such viewpoints, it is preferable that theplurality of III-nitride crystal substrates 10 p, 10 q and theIII-nitride crystal 20 that is grown be of the same chemicalcomposition. Making that the case enables III-nitride crystal 20 ofsuperior crystallinity, having a {h₀k₀i₀l₀} major surface 20 m, to bemanufactured.

In a III-nitride crystal manufacturing method in the present embodyingmode, the aforementioned {h₀k₀i₀l₀} preferably is anycrystallographically equivalent plane orientation selected from thegroup consisting of {1-10x} (wherein x is a whole number), {11-2y}(wherein y is a whole number), and {hk-(h+k)l} (wherein h, k and l arewhole numbers). In III-nitride crystal thus conditioned, a face havingany of the plane orientations {1-10x}, {11-2y}, or {hk-(h+k)l} is astable face, and therefore, III-nitride crystal of superiorcrystallinity can be grown stably onto a major surface having such planeorientation.

Again {h₀k₀i₀l₀} may be, if not any crystallographically equivalentplane orientation selected from the group consisting of {1-10x},{11-2y}, and {hk-(h+k)l}, then off-axis by an angle of 5° or less withrespect to whichever of these plane orientations. A plane orientationthat is misoriented 5° or less with respect to any crystallographicallyequivalent plane orientation selected from the group consisting of{1-10x}, {11-2y}, and {hk-(h+k)l} enables crystal growth in the samemanner as in {1-10x}, {11-2y}, or {hk-(h+k)l} instances, and thereforeIII-nitride crystal of superior crystallinity can be grown stably onto amajor surface with such plane orientation. Herein, “off-axis angle”means the angle that any given plane orientation and any other planeorientation form, and is measured by x-ray crystallography.

For reference in the present description, specific examples of {1-10x}planes (x: a whole number), {11-2y} planes (y: a whole number), and {hk-(h+k)l} planes (h, k and l: whole numbers) in a unit cell of III-nitridecrystal that is hexagonal are depicted in FIGS. 15 through 17. Herein,the arrows a₁, a₂, a₃ and c are crystal axes for the cell unit of thehexagonal III-nitride crystal.

A face having any crystallographically equivalent plane orientationselected from the group consisting of {1-10x}, {11-2y}, and {hk-(h+k)l}is in III-nitride crystal a stable face. In the growth of III-nitridecrystal, characteristic of the high crystal growth rates afforded byvapor deposition, especially HVPE techniques, is that crystal growth inthe c-axis direction (i.e., the [0001] direction) is rapid.Consequently, in III-nitride crystal grown by vapor-phase techniquessuch as HVPE, the (1-10±1) faces, the (1-10±2) faces, the (11-2±1)faces, the (11-2±2) faces, the (20-2±1) faces and the (22-4±1) facesprove to be more stable. On the other hand, because the crystal growthrate with liquid-phase growth is low, in III-nitride crystal grown byliquid-phase techniques, the (1-10±3) faces and the (11-2±3) faces proveto be more stable. It will be understood that owing to thecumbersomeness of writing out the notation for both the (10-11) face andthe (10-1-1), the notations have been abbreviated as the “(10-1±1)”faces. The notations for the other plane orientations have beenabbreviated in the same way.

In a III-nitride crystal manufacturing method in the present embodyingmode, it is preferable that the aforementioned {h₀k₀i₀l₀} be anycrystallographically equivalent plane orientation selected from thegroup consisting of {1-100}, {11-20}, {1-10±2}, {11-2±2}, {20-2±1} and{22-4±1}. Herein, because III-nitride crystal faces whose planeorientations are {1-100}, {11-20}, {1-10±2}, {11-2±2}, {20-2±1} or{22-4±1} are stable faces, III-nitride crystal of superior crystallinitycan be grown stably onto a major surface with such plane orientation.

Again {h₀k₀i₀l₀} may be, rather than any crystallographically equivalentplane orientation selected from the group consisting of {1-100},{11-20}, {1-10±2}, {11-2±2}, {20-2±1} and {22-4±1}, an off-axis angle of5° or less with respect to whichever of these plane orientations. Aplane orientation that is misoriented 5° or less with respect to anycrystallographically equivalent plane orientation selected from thegroup consisting of {1-100}, {11-20}, {1-10±2}, {11-2±2}, {20-2±1} and{22-4±1} enables crystal growth in the same manner as in {1-100},{11-20}, {1-10±2}, {11-2±2}, {20-2±1} and {22-4±1} instances, andtherefore III-nitride crystal of superior crystallinity can be grownstably onto a major surface with such plane orientation.

It is also preferable in a III-nitride crystal manufacturing method inthe present embodying mode that {h₀k₀i₀l₀} be {1-100}. In III-nitridecrystal, {1-100} is a stable plane and at the same time is a cleavageplane; therefore, III-nitride crystal of superior crystallinity can bestably grown, and by cleaving the grown III-nitride crystal along the{1-100} planes, III-nitride crystal substrates of superiorcrystallinity, having a major surface of {1-100} plane orientation canbe readily produced.

Again {h₀k₀i₀l₀} may be, rather than {1-100}, an off-axis angle of 5° orless with respect to this plane orientation. Being misoriented 5° orless with respect to {1-100} enables crystal growth in the same manneras in implementations on {1-100}, and therefore III-nitride crystal ofsuperior crystallinity can be grown stably onto a major surface withsuch plane orientation.

Furthermore, in a III-nitride crystal manufacturing method in thepresent embodying mode, the roughness average Ra of faces 10 pt, 10 qtalong which the plurality of III-nitride crystal substrates 10 p, 10 qadjoin each other (here, and likewise below, termed “adjoining faces 10pt, 10 qt”) preferably is 50 nm or less, more preferably 5 nm or less.If the roughness average Ra of the adjoining faces 10 pt, 10 qt exceeds50 nm, the crystallinity of the region 20 t in the III-nitride crystal20 above the adjoining faces 10 pt, 10 qt and their proximity (whichwill be termed “adjoining-substrate supra-region 20 t”) will becompromised. Here, “roughness average Ra of a surface” means arithmeticmean roughness Ra, defined in JIS B 0601, and specifically it refers tosampling “cutoff” lengths from a roughness profile along its mean line,and summing, and averaging by cutoff length, distances (the absolutevalue of deviations) from the mean line to the roughness profile in thesampling section. The surface roughness average Ra can be measuredemploying an atomic force microscope (AFM) and so on.

In a III-nitride crystal manufacturing method in the present embodyingmode, then, in order to have the roughness average Ra of the adjoiningfaces 10 pt, 10 qt of the plurality of III-nitride crystal substrates 10p, 10 q be 50 nm or less, after the first step (slice-off substratesstep) and before the second step (substrate placement step), a step ofgrinding and/or polishing the edge faces that will become the adjoiningfaces 10 pt, 10 qt of the plurality of III-nitride crystal substrates 10p, 10 q (also termed grinding/polishing step hereinafter) preferably isincluded.

Also in a III-nitride crystal manufacturing method in the presentembodying mode, from the perspective of further enhancing thecrystallinity of the III-nitride crystal that is grown, after the firststep (slice-off substrates step) and before the second step (substrateplacement step), a step of grinding and/or polishing (grinding/polishingstep) the {h₀k₀i₀l₀} major surfaces 10 pm, 10 qm—which are the surfacesonto which the III-nitride crystal is grown—of the plurality ofIII-nitride crystal substrates 10 p, 10 q preferably is included. It ispreferable that the surface roughness of the {h₀k₀i₀l₀} major surfaces10 pm, 10 qm resulting from such grinding/polishing step be 50 nm orless; that the roughness be 5 nm is more preferable.

Another advantageous condition in a III-nitride crystal manufacturingmethod in the present embodying mode is that the temperature at whichthe III-nitride crystal 20 is grown be 2000° C. or more. This is becausewith III-nitride crystal grown at a temperature of 2000° C. or more, thecrystallinity proves to be uniform globally across the surface where thecrystal is grown. Here, “crystallinity is uniform” signifies that thefull-width-at-half-maximum in-plane profile of the peak resulting froman x-ray diffraction rocking-curve analysis of the {h₀k₀i₀l₀} face isnarrow, and that the dislocation-density in-plane distribution asquantified by cathodoluminescence spectroscopy (CL) or etch-pit density(EP) measurement is narrow.

A still further advantageous condition in a III-nitride crystalmanufacturing method in the present embodying mode is that the methodwhereby the III-nitride crystal 20 is grown be sublimation growth. Thisis because by sublimation methods, III-nitride crystal is grown attemperatures of 2000° C. or more, and therefore the crystallinity of theIII-nitride crystal that is grown proves to be uniform globally acrossthe crystal-growth surface.

Embodiments

III-Nitride Bulk Crystal Preparation 1

GaN bulk crystal, as III-nitride bulk crystal utilized in a III-nitridecrystal manufacturing method involving the present invention, wasmanufactured by a method as below, wherein reference is made to FIG. 2.

Initially, an SiO₂ layer of 100 nm thickness was formed as a mask layer91 by sputter deposition onto, as an undersubstrate 90, a GaAs substrateof 50 mm diameter, 0.8 mm thickness, having a (111) A-plane majorsurface. Next, windows 91 w, as illustrated FIGS. 2A and 2B, whosediameter D was 2 μm were formed in the mask by photolithography andetching, arrayed at a pitch P of 4 μm in a close-hexagonal packingpattern. In this case the GaAs substrate 90 was exposed through thewindows 91 w.

Next, GaN bulk crystal, as III-nitride bulk crystal, was grown by HVPEonto the GaAs substrate 90 on which the mask 91 having a plurality ofthe windows 91 w had been formed. Specifically, a GaN low-temperaturelayer of 80 nm thickness was grown by HVPE at 500° C. onto the GaAssubstrate, onto that layer subsequently a GaN intermediate layer of 60μm thickness was grown at 950° C., after which GaN bulk crystal of 5 mmthickness was grown at 1050° C. onto the intermediate layer.

Next, the GaAs substrate was removed from the GaN bulk crystal by anetching process employing aqua regia, to yield GaN bulk crystal of 50 mmdiameter and 3 mm thickness, as III-nitride bulk crystal.

Embodiment 1

To begin with, referring to FIG. 3A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm. Here measurement of the surface roughnessaverage Ra was carried out by AFM.

Next, referring to FIG. 3A, the GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 5 nm was sawed along a plurality of planes perpendicularto a <1-100> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was3 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having {1-100}major surfaces. Subsequently, the not-ground and not-polished four sidesof each sliced-off GaN crystal substrate were ground and polished, tobring the roughness average Ra of the four surfaces to 5 nm. A pluralityof GaN crystal substrates whose roughness average Ra on the {1-100}major surfaces was 5 nm was thus obtained. Among these GaN crystalsubstrates were GaN crystal substrates whose major-surface planeorientation did not coincide perfectly with {1-100}, but the planeorientation of the major surface of such GaN crystal substrates in allcases was misoriented by 5° or less with respect to {1-100}. Here, theoff-axis angle was measured by x-ray crystallography.

Next, referring to FIG. 3B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (1-100) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be oriented in thesame way. In this instance, referring also to FIG. 3C, the roughnessaverage Ra of the adjoining faces 10 pt, 10 qt of the plurality of GaNcrystal substrates (III-nitride crystal substrates 10 p, 10 q) was 5 nm.

Next, with reference again to FIG. 3C, the (1-100) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed for two hours at 800° C.under an atmosphere that was a gaseous mixture of 10 volume % hydrogenchloride and 90 volume % nitrogen, and afterwards, by HVPE and at acrystal growth temperature of 1050° C., GaN crystal (epitaxialIII-nitride crystal 20) was grown onto the major surfaces 10 pm, 10 qmfor 50 hours at a deposition rate of 20 μm/hr, yielding a III-nitridecrystal composite.

The obtained GaN crystal (epitaxial III-nitride crystal 20), free ofabnormal growth even in the adjoining-substrate supra-regions 20 t, hada (1-100) major surface 20 m. The crystallinity of the GaN crystal(epitaxial III-nitride crystal 20) was characterized by an x-raydiffraction rocking-curve analysis of the (1-100) plane. With this GaNcrystal, the direct-over-substrate regions 20 s (meaning—likewisehereinafter—the regions 20 s that are directly above the pluralIII-nitride crystal substrates 10 p, 10 q), demonstrated diffractionpeaks undivided in the tip, with the full-width at half-maximum being100 arcsec. In the adjoining-substrate supra-regions 20 t, meanwhile,diffraction peaks with divisions in the tip were demonstrated, with thefull-width at half-maximum being 300 arcsec. It should be understoodthat a “principal impurity(ies)” as given in the present specificationis an impurity(ies) that is present in an amount occupying at least 95%among the entirety of impurities in the III-nitride crystal. Saying “theprincipal impurities are oxygen atoms and silicon atoms” means “oxygenatoms (O) and silicon atoms (Si) occupy at least 95% among the entiretyof the impurities in the III-nitride crystal.”

Furthermore, threading dislocation density in the (1-100) major surface20 m of the GaN crystal was determined by cathodoluminescencespectroscopy (termed “CL” hereinafter), whereupon the density was 1×10⁷cm⁻² in the direct-over-substrate regions 20 s, and 3×10⁷ cm⁻² in theadjoining-substrate supra-regions 20 t. In addition, the carrierconcentration in the GaN crystal was determined by Hall-effectmeasurements, whereupon it was 5×10¹⁸ cm⁻³. And the principal impuritiesin the GaN crystal according to SIMS (secondary ion mass spectrometry,likewise hereinafter) were oxygen (O) atoms and silicon (Si) atoms. Theresults are tabulated in Table I.

It should be understood that in Embodiment 1, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (1-100), in thatalthough a few or more might have been (−1100), the crystallographicequivalent of (1-100), they would lead to the same results.

Embodiment 2

Reference is again made to FIG. 3A: Apart from grinding and polishingthe (0001) face and (000-1) face—the two major surfaces—of GaN bulkcrystal (III-nitride bulk crystal 1) to bring the roughness average Raof either major surface to 50 nm, in the same manner as in Embodiment 1,plural GaN crystal substrates (III-nitride crystal substrates 10 p, 10q) were sliced off, and the not-ground and not-polished four sides ofeach GaN crystal substrate were ground and polished, to bring theroughness average Ra of the four surfaces to 5 nm. Among the pluralityof GaN crystal substrates were GaN crystal substrates whosemajor-surface plane orientation did not coincide perfectly with {1-100},but the plane orientation of the major surface of such GaN crystalsubstrates in all cases was misoriented by 5° or less with respect to{1-100}.

Next, referring to FIG. 3B, the plural GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) were situated in the samemanner as in Embodiment 1. In this case, referring also to FIG. 4, theroughness average Ra of the adjoining faces 10 pt, 10 qt of theplurality of GaN crystal substrates was 50 nm.

Next, with reference again to FIG. 4: The (1-100) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal (III-nitride crystal 20) had a (1-100) majorsurface 20 m in which pits 20 v constituted by a plurality of facets 20f were formed in the adjoining-substrate supra-regions 20 t. Further, inan x-ray diffraction rocking-curve analysis of the (1-100) plane of theGaN crystal (III-nitride crystal 20), the direct-over-substrate regions20 s demonstrated diffraction peaks undivided in the tip, with thefull-width at half-maximum being 100 arcsec. In the adjoining-substratesupra-regions 20 t, meanwhile, diffraction peaks with divisions in thetip were demonstrated, with the full-width at half-maximum being 800arcsec.

Furthermore, threading dislocation density in the (1-100) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 8×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 5×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 2, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (1-100), in thatalthough a few or more might have been (−1100), the crystallographicequivalent of (1-100), they would lead to the same results.

Embodiment 3

To begin with, referring to FIG. 5A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 5A: The GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 5 nm was sawed along a plurality of planes perpendicularto a <11-20> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was3 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having {11-20}major surfaces. Subsequently, the not-ground and not-polished four sidesof each sliced-off GaN crystal substrate were ground and polished, tobring the roughness average Ra of the four surfaces to 5 nm. A pluralityof GaN crystal substrates whose roughness average Ra on the {11-20}major surfaces was 5 nm was thus obtained. Among these GaN crystalsubstrates were GaN crystal substrates whose major-surface planeorientation did not coincide perfectly with {11-20}, but the planeorientation of the major surface of such GaN crystal substrates in allcases was misoriented by 5° or less with respect to {11-20}.

Next, referring to FIG. 5B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (11-20) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 5C, the roughness average Ra of the adjoining faces 10 pt, 10 qt ofthe plurality of GaN crystal substrates was 5 nm.

Next, with reference again to FIG. 5C: The (11-20) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal (III-nitride crystal 20) had a (11-20) majorsurface 20 m in which pits 20 v defined by a plurality of facets 20 fwere formed in the adjoining-substrate supra-regions 20 t. Further, inan x-ray diffraction rocking-curve analysis of the (11-20) plane of theGaN crystal (III-nitride crystal 20), the direct-over-substrate regions20 s demonstrated diffraction peaks undivided in the tip, with thefull-width at half-maximum being 250 arcsec. In the adjoining-substratesupra-regions 20 t, meanwhile, diffraction peaks with divisions in thetip were demonstrated, with the full-width at half-maximum being 620arcsec.

Furthermore, threading dislocation density in the (11-20) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 8×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 5×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 3, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (11-20), in thatalthough a few or more might have been (−1-120), the crystallographicequivalent of (11-20), they would lead to the same results.

Embodiment 4

To begin with, referring to FIG. 6A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground to bring the roughness average Ra of either majorsurface to 50 nm.

Next, again referring to FIG. 6A: The GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 50 nm was sawed along a plurality of planes perpendicularto a <1-102> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was5 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having {1-102}major surfaces. Subsequently, the six sides of each sliced-off GaNcrystal substrate were ground and polished, to bring the surfaces'roughness average Ra to 5 nm. A plurality of GaN crystal substrateswhose roughness average Ra on the {1-102} major surfaces was 5 nm wasthus obtained. Among these GaN crystal substrates were GaN crystalsubstrates whose major-surface plane orientation did not coincideperfectly with {1-102}, but the plane orientation of the major surfaceof such GaN crystal substrates in all cases was misoriented by 5° orless with respect to {1-102}.

Next, referring to FIG. 6B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (1-102) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 6C, the roughness average Ra of the adjoining faces 10 pt, 10 qt ofthe plurality of GaN crystal substrates was 5 nm.

Next, with reference again to FIG. 6C: The (1-102) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal, free of abnormal growth even in theadjoining-substrate supra-regions 20 t, had a (1-102) major surface 20m. In an x-ray diffraction rocking-curve analysis of the (1-102) planeof the GaN crystal (III-nitride crystal 20), the direct-over-substrateregions 20 s demonstrated diffraction peaks undivided in the tip, withthe full-width at half-maximum being 120 arcsec. In theadjoining-substrate supra-regions 20 t, meanwhile, diffraction peakswith divisions in the tip were demonstrated, with the full-width athalf-maximum being 480 arcsec.

Furthermore, threading dislocation density in the (1-102) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 6×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 5×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 4, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (1-102), in thatalthough a few or more might have been (−1102), the crystallographicequivalent of (1-102), they would lead to the same results.

Embodiment 5

To begin with, referring to FIG. 6A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground to bring the roughness average Ra of either majorsurface to 50 nm.

Next, again referring to FIG. 6A: The GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 50 nm was sawed along a plurality of planes perpendicularto a <1-10−2> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was5 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having{1-10−2} major surfaces. Subsequently, the six sides of each sliced-offGaN crystal substrate were ground and polished, to bring the surfaces'roughness average Ra to 5 nm. A plurality of GaN crystal substrateswhose roughness average Ra on the {1-10−2} major surfaces was 5 nm wasthus obtained. Among these GaN crystal substrates were GaN crystalsubstrates whose major-surface plane orientation did not coincideperfectly with {1-10−2}, but the plane orientation of the major surfaceof such GaN crystal substrates in all cases was misoriented by 5° orless with respect to {1-10−2}.

Next, referring to FIG. 6D, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (1-10−2) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 6C, the roughness average Ra of the adjoining faces 10 pt, 10 qt ofthe plurality of GaN crystal substrates was 5 nm.

With reference now to FIG. 6E: Next, the (1-10−2) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal, free of abnormal growth even in theadjoining-substrate supra-regions 20 t, had a (1-10−2) major surface 20m. In an x-ray diffraction rocking-curve analysis of the (1-10−2) planeof the GaN crystal (III-nitride crystal 20), the direct-over-substrateregions 20 s demonstrated diffraction peaks undivided in the tip, withthe full-width at half-maximum being 100 arcsec. In theadjoining-substrate supra-regions 20 t, meanwhile, diffraction peakswith divisions in the tip were demonstrated, with the full-width athalf-maximum being 420 arcsec.

Furthermore, threading dislocation density in the (1-10−2) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 6×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 5×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 5, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (1-10−2), in thatalthough a few or more might have been (−110-2), the crystallographicequivalent of (1-10−2), they would lead to the same results.

Embodiment 6

To begin with, referring to FIG. 7A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground to bring the roughness average Ra of either majorsurface to 50 nm.

Next, again referring to FIG. 7A: The GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 50 nm was sawed along a plurality of planes perpendicularto a <11-22> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was5 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having {11-22}major surfaces. Subsequently, the six sides of each sliced-off GaNcrystal substrate were ground and polished, to bring the roughnessaverage Ra of the six surfaces to 5 nm. A plurality of GaN crystalsubstrates whose roughness average Ra on the {11-22} major surfaces was5 nm was thus obtained. Among these GaN crystal substrates were GaNcrystal substrates whose major-surface plane orientation did notcoincide perfectly with {11-22}, but the plane orientation of the majorsurface of such GaN crystal substrates in all cases was misoriented by5° or less with respect to {11-22}.

Next, referring to FIG. 7B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (11-22) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, the roughnessaverage Ra of the adjoining faces 10 pt, 10 qt of the plurality of GaNcrystal substrates was 5 nm.

Next, with reference to FIG. 7C: The (11-22) major surfaces 10 pm, 10 qmof the situated plurality of GaN crystal substrates (III-nitride crystalsubstrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal, free of abnormal growth even in theadjoining-substrate supra-regions 20 t, had a (11-22) major surface 20m. In an x-ray diffraction rocking-curve analysis of the (11-22) planeof the GaN crystal (III-nitride crystal 20), the direct-over-substrateregions 20 s demonstrated diffraction peaks undivided in the tip, withthe full-width at half-maximum being 90 arcsec. In theadjoining-substrate supra-regions 20 t, meanwhile, diffraction peakswith divisions in the tip were demonstrated, with the full-width athalf-maximum being 380 arcsec.

Furthermore, threading dislocation density in the (11-22) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 4×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 5×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 6, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (11-22), in thatalthough a few or more might have been (−2112), the crystallographicequivalent of (11-22), they would lead to the same results.

Embodiment 7

To begin with, referring to FIG. 7A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground to bring the roughness average Ra of either majorsurface to 50 nm.

Next, again referring to FIG. 7A: The GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 50 nm was sawed along a plurality of planes perpendicularto a <11-2−2> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was5 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having{11-2−2} major surfaces. Subsequently, the six sides of each sliced-offGaN crystal substrate were ground and polished, to bring the roughnessaverage Ra of the six surfaces to 5 nm. A plurality of GaN crystalsubstrates whose roughness average Ra on the {11-2−2} major surfaces was5 nm was thus obtained. Among these GaN crystal substrates were GaNcrystal substrates whose major-surface plane orientation did notcoincide perfectly with {11-2−2}, but the plane orientation of the majorsurface of such GaN crystal substrates in all cases was misoriented by5° or less with respect to {11-2−2}.

Next, referring to FIG. 7D, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (11-2−2) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, the roughnessaverage Ra of the adjoining faces 10 pt, 10 qt of the plurality of GaNcrystal substrates was 5 nm.

With reference now to FIG. 7E: Next, the (11-2−2) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal, free of abnormal growth even in theadjoining-substrate supra-regions 20 t, had a (11-2−2) major surface 20m. In an x-ray diffraction rocking-curve analysis of the (11-2−2) planeof the GaN crystal (III-nitride crystal 20), the direct-over-substrateregions 20 s demonstrated diffraction peaks undivided in the tip, withthe full-width at half-maximum being 80 arcsec. In theadjoining-substrate supra-regions 20 t, meanwhile, diffraction peakswith divisions in the tip were demonstrated, with the full-width athalf-maximum being 360 arcsec.

Furthermore, threading dislocation density in the (11-2−2) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 4×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 5×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 7, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (11-2−2), in thatalthough a few or more might have been (−211−2), the crystallographicequivalent of (11-2−2), they would lead to the same results.

Embodiment 8

To begin with, referring to FIG. 8A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 8A: The GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 5 nm was sawed along a plurality of planes perpendicularto a <12-30> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was3 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having {12-30}major surfaces. Subsequently, the not-ground and not-polished four sidesof each sliced-off GaN crystal substrate were ground and polished, tobring the roughness average Ra of the four surfaces to 5 nm. A pluralityof GaN crystal substrates whose roughness average Ra on the {12-30}major surfaces was 5 nm was thus obtained. Among these GaN crystalsubstrates were GaN crystal substrates whose major-surface planeorientation did not coincide perfectly with {12-30}, but the planeorientation of the major surface of such GaN crystal substrates in allcases was misoriented by 5° or less with respect to {12-30}.

Next, referring to FIG. 8B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (12-30) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 8C, the roughness average Ra of the adjoining faces 10 pt, 10 qt ofthe plurality of GaN crystal substrates was 5 nm.

Next, with reference again to FIG. 8C: The (12-30) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal (III-nitride crystal 20) had a (12-30) majorsurface 20 m in which pits 20 v constituted by a plurality of facets 20f were formed in the adjoining-substrate supra-regions 20 t. Further, inan x-ray diffraction rocking-curve analysis of the (12-30) plane of theGaN crystal (III-nitride crystal 20), the direct-over-substrate regions20 s demonstrated diffraction peaks undivided in the tip, with thefull-width at half-maximum being 280 arcsec. In the adjoining-substratesupra-regions 20 t, meanwhile, diffraction peaks with divisions in thetip were demonstrated, with the full-width at half-maximum being 660arcsec.

Furthermore, threading dislocation density in the (12-30) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 7×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 4×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 8, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (12-30), in thatalthough a few or more might have been (−3210), the crystallographicequivalent of (12-30), they would lead to the same results.

Embodiment 9

To begin with, referring to FIG. 9A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 9A: The GaN bulk crystal (III-nitride bulkcrystal 1) whose roughness average Ra on either of its major surfaceshad been made 5 nm was sawed along a plurality of planes perpendicularto a <23-50> direction to slice off a plurality of GaN crystalsubstrates (III-nitride crystal substrates 10 p, 10 q) whose width S was3 mm, length L was 20 to 50 mm, and thickness T was 1 mm, having {23-50}major surfaces. Subsequently, the not-ground and not-polished four sidesof each sliced-off GaN crystal substrate were ground and polished, tobring the roughness average Ra of the four surfaces to 5 nm. A pluralityof GaN crystal substrates whose roughness average Ra on the {23-50}major surfaces was 5 nm was thus obtained. Among these GaN crystalsubstrates were GaN crystal substrates whose major-surface planeorientation did not coincide perfectly with {23-50}, but the planeorientation of the major surface of such GaN crystal substrates in allcases was misoriented by 5° or less with respect to {23-50}.

Next, referring to FIG. 9B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (23-50) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, the roughnessaverage Ra of the adjoining faces 10 pt, 10 qt of the plurality of GaNcrystal substrates was 5 nm.

With reference now to FIG. 9C: Next, GaN crystal (III-nitride crystal20) was deposited by flux growth onto the (23-50) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q). Specifically, a Ga—Na melt (a liquefiedmixture of Ga and Na) was contacted on the (23-50) major surfaces 10 pm,10 qm of the plurality of GaN crystal substrates, and undercrystal-growth temperature and crystal-growth pressure (gaseous-nitrogenpressure) conditions of 870° C. and 4 MPa (40 atmospheres), GaN crystal(III-nitride crystal 20) was grown onto the (23-50) major surfaces 10pm, 10 qm of the GaN crystal substrates for 100 hours at a depositionrate of 5 μm/hr.

The obtained GaN crystal, free of abnormal growth even in theadjoining-substrate supra-regions 20 t, had a (23-50) major surface 20m. In an x-ray diffraction rocking-curve analysis of the (23-50) planeof the GaN crystal (III-nitride crystal 20), the direct-over-substrateregions 20 s demonstrated diffraction peaks undivided in the tip, withthe full-width at half-maximum being 230 arcsec. In theadjoining-substrate supra-regions 20 t, meanwhile, diffraction peakswith divisions in the tip were demonstrated, with the full-width athalf-maximum being 490 arcsec.

Furthermore, threading dislocation density in the (23-50) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 4×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 3×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 9, the plane orientations ofthe major surfaces 10 pm, 10 qm of the plurality of GaN crystalsubstrates that were the surfaces onto which the GaN crystal was grownwere all (23-50), in that although a few or more might have been(−5230), the crystallographic equivalent of (23-50), they would lead tothe same results.

Embodiment 10

To begin with, referring to FIG. 10A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 10A: The GaN bulk crystal (III-nitridebulk crystal 1) whose roughness average Ra on either of its majorsurfaces had been made 5 nm was sawed along a plurality of planesperpendicular to a <20-21> direction to slice off a plurality of GaNcrystal substrates (III-nitride crystal substrates 10 p, 10 q) whosewidth S was 3 mm, length L was 20 to 50 mm, and thickness T was 1 mm,having {20-21} major surfaces. Subsequently, the not-ground andnot-polished four sides of each sliced-off GaN crystal substrate wereground and polished, to bring the roughness average Ra of the foursurfaces to 5 nm. A plurality of GaN crystal substrates whose roughnessaverage Ra on the {20-21} major surfaces was 5 nm was thus obtained.Among these GaN crystal substrates were GaN crystal substrates whosemajor-surface plane orientation did not coincide perfectly with {20-21},but the plane orientation of the major surface of such GaN crystalsubstrates in all cases was misoriented by 5° or less with respect to{20-21}.

Next, referring to FIG. 10B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (20-21) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 10C, the roughness average Ra of the adjoining faces 10 pt, 10 qtof the plurality of GaN crystal substrates was 5 nm.

Next, with reference again to FIG. 10C: The (20-21) major surfaces 10pm, 10 qm of the situated plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) were processed in the sameway as that of Embodiment 1, and thereafter GaN crystal (III-nitridecrystal 20) was grown onto the major surfaces 10 pm, 10 qm under thesame conditions as those of Embodiment 1.

The obtained GaN crystal, free of abnormal growth even in theadjoining-substrate supra-regions 20 t, had a (20-21) major surface 20m. In an x-ray diffraction rocking-curve analysis of the (20-21) planeof the GaN crystal (III-nitride crystal 20), the direct-over-substrateregions 20 s demonstrated diffraction peaks undivided in the tip, withthe full-width at half-maximum being 120 arcsec. In theadjoining-substrate supra-regions 20 t, meanwhile, diffraction peaksthat with divisions in the tip were demonstrated, with the full-width athalf-maximum being 380 arcsec.

Furthermore, threading dislocation density in the (20-21) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 4×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 1×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 10, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (20-21), in thatalthough a few or more might have been (−2021), the crystallographicequivalent of (20-21), they would lead to the same results.

Embodiment 11

To begin with, referring to FIG. 10A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 10A: The GaN bulk crystal (III-nitridebulk crystal 1) whose roughness average Ra on either of its majorsurfaces had been made 5 nm was sawed along a plurality of planesperpendicular to a <20-2−1> direction to slice off a plurality of GaNcrystal substrates (III-nitride crystal substrates 10 p, 10 q) whosewidth S was 3 mm, length L was 20 to 50 mm, and thickness T was 1 mm,having {20-2−1} major surfaces. Subsequently, the not-ground andnot-polished four sides of each sliced-off GaN crystal substrate wereground and polished, to bring the roughness average Ra of the foursurfaces to 5 nm. A plurality of GaN crystal substrates whose roughnessaverage Ra on the {20-2−1} major surfaces was 5 nm was thus obtained.Among these GaN crystal substrates were GaN crystal substrates whosemajor-surface plane orientation did not coincide perfectly with{20-2−1}, but the plane orientation of the major surface of such GaNcrystal substrates in all cases was misoriented by 5° or less withrespect to {20-2−1}.

Next, referring to FIG. 10D, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (20-2−1) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 10C, the roughness average Ra of the adjoining faces 10 pt, 10 qtof the plurality of GaN crystal substrates was 5 nm.

With reference now to FIG. 10E: Next, the (20-2−1) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal, free of abnormal growth even in theadjoining-substrate supra-regions 20 t, had a (20-2−1) major surface 20m. In an x-ray diffraction rocking-curve analysis of the (20-2−1) planeof the GaN crystal (III-nitride crystal 20), the direct-over-substrateregions 20 s demonstrated diffraction peaks undivided in the tip, withthe full-width at half-maximum being 90 arcsec. In theadjoining-substrate supra-regions 20 t, meanwhile, diffraction peakswith divisions in the tip were demonstrated, with the full-width athalf-maximum being 360 arcsec.

Furthermore, threading dislocation density in the (20-2−1) major surface20 m of the GaN crystal was 1×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 4×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 1×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 11, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (20-2−1), in thatalthough a few or more might have been (−202−1), the crystallographicequivalent of (20-2−1), they would lead to the same results.

Embodiment 12

To begin with, referring to FIG. 11A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 11A: The GaN bulk crystal (III-nitridebulk crystal 1) whose roughness average Ra on either of its majorsurfaces had been made 5 nm was sawed along a plurality of planesperpendicular to a <22-41> direction to slice off a plurality of GaNcrystal substrates (III-nitride crystal substrates 10 p, 10 q) whosewidth S was 3 mm, length L was 20 to 50 mm, and thickness T was 1 mm,having {22-41} major surfaces. Subsequently, the not-ground andnot-polished four sides of each sliced-off GaN crystal substrate wereground and polished, to bring the roughness average Ra of the foursurfaces to 5 nm. A plurality of GaN crystal substrates whose roughnessaverage Ra on the {22-41} major surfaces was 5 nm was thus obtained.Among these GaN crystal substrates were GaN crystal substrates whosemajor-surface plane orientation did not coincide perfectly with {22-41},but the plane orientation of the major surface of such GaN crystalsubstrates in all cases was misoriented by 5° or less with respect to{22-41}.

Next, referring to FIG. 11B, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (22-41) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 11C, the roughness average Ra of the adjoining faces 10 pt, 10 qtof the plurality of GaN crystal substrates was 5 nm.

Next, with reference again to FIG. 11C: The (22-41) major surfaces 10pm, 10 qm of the situated plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) were processed in the sameway as that of Embodiment 1, and thereafter GaN crystal (III-nitridecrystal 20) was grown onto the major surfaces 10 pm, 10 qm under thesame conditions as those of Embodiment 1.

The obtained GaN crystal (III-nitride crystal 20) had a (22-41) majorsurface 20 m in which pits 20 v defined by a plurality of facets 20 fwere formed in the adjoining-substrate supra-regions 20 t. Further, inan x-ray diffraction rocking-curve analysis of the (22-41) plane of theGaN crystal (III-nitride crystal 20), the direct-over-substrate regions20 s demonstrated diffraction peaks undivided in the tip, with thefull-width at half-maximum being 220 arcsec. In the adjoining-substratesupra-regions 20 t, meanwhile, diffraction peaks with divisions in thetip were demonstrated, with the full-width at half-maximum being 580arcsec.

Furthermore, threading dislocation density in the (22-41) major surface20 m of the GaN crystal was 3×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 7×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 2×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 12, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (22-41), in thatalthough a few or more might have been (−4221), the crystallographicequivalent of (22-41), they would lead to the same results.

Embodiment 13

To begin with, referring to FIG. 11A, the (0001) face and (000-1)face—the two major surfaces—of GaN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 11A: The GaN bulk crystal (III-nitridebulk crystal 1) whose roughness average Ra on either of its majorsurfaces had been made 5 nm was sawed along a plurality of planesperpendicular to a <22-4−1> direction to slice off a plurality of GaNcrystal substrates (III-nitride crystal substrates 10 p, 10 q) whosewidth S was 3 mm, length L was 20 to 50 mm, and thickness T was 1 mm,having {22-4−1} major surfaces. Subsequently, the not-ground andnot-polished four sides of each sliced-off GaN crystal substrate wereground and polished, to bring the roughness average Ra of the foursurfaces to 5 nm. A plurality of GaN crystal substrates whose roughnessaverage Ra on the {22-4−1} major surfaces was 5 nm was thus obtained.Among these GaN crystal substrates were GaN crystal substrates whosemajor-surface plane orientation did not coincide perfectly with{22-4−1}, but the plane orientation of the major surface of such GaNcrystal substrates in all cases was misoriented by 5° or less withrespect to {22-4−1}.

Next, referring to FIG. 11D, these GaN crystal substrates were disposedadjoining each other sideways, in a manner such that the (22-4−1) majorsurfaces 10 pm, 10 qm of the plurality of GaN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the GaN crystal substrateswould be conformed. In this instance, referring also to FIG. 11C, theroughness average Ra of the adjoining faces 10 pt, 10 qt of theplurality of GaN crystal substrates was 5 nm.

With reference now to FIG. 11E: Next, the (22-4−1) major surfaces 10 pm,10 qm of the situated plurality of GaN crystal substrates (III-nitridecrystal substrates 10 p, 10 q) were processed in the same way as that ofEmbodiment 1, and thereafter GaN crystal (III-nitride crystal 20) wasgrown onto the major surfaces 10 pm, 10 qm under the same conditions asthose of Embodiment 1.

The obtained GaN crystal (III-nitride crystal 20) had a (22-4−1) majorsurface 20 m in which pits 20 v defined by a plurality of facets 20 fwere formed in the adjoining-substrate supra-regions 20 t. Further, inan x-ray diffraction rocking-curve analysis of the (22-4−1) plane of theGaN crystal (III-nitride crystal 20), the direct-over-substrate regions20 s demonstrated diffraction peaks undivided in the tip, with thefull-width at half-maximum being 200 arcsec. In the adjoining-substratesupra-regions 20 t, meanwhile, diffraction peaks with divisions in thetip were demonstrated, with the full-width at half-maximum being 480arcsec.

Furthermore, threading dislocation density in the (22-4−1) major surface20 m of the GaN crystal was 3×10⁷ cm⁻² in the direct-over-substrateregions 20 s, and 7×10⁷ cm⁻² in the adjoining-substrate supra-regions 20t. In addition, the carrier concentration in the GaN crystal was 2×10¹⁸cm⁻³, while the principal impurities were oxygen atoms and siliconatoms. The results are tabulated in Table I.

It should be understood that in Embodiment 13, the major-surface planeorientations of the plurality of GaN crystal substrates that were thesurfaces onto which the GaN crystal was grown were all (22-4−1), in thatalthough a few or more might have been (−422−1), the crystallographicequivalent of (22-4−1), they would lead to the same results.

TABLE I Emb. 1 Emb. 2 Emb. 3 Emb. 4 Emb. 5 Emb. 6 Emb. 7 III-NitrideSubstrate type GaN GaN GaN GaN GaN GaN GaN crystal substrateMajor-surface (1 100) (1 100) (11 20) (1 102) (1 10 2) (11 22) (11 22)plane orient. Major-surface   5   5   5   5   5   5   5 roughness Ra(nm) Adjoining-surface   5  50   5   5   5   5   5 roughness Ra (nm)III-Nitride crystal Crystal type GaN GaN GaN GaN GaN GaN GaN Crystalgrowth method HVPE HVPE HVPE HVPE HVPE HVPE HVPE Crystal growth 10501050 1050 1050 1050 1050 1050 temperature (° C.) Major-surface (1 100)(1 100) (11 20) (1 102) (1 10 2) (11 22) (11 22) plane orient. Pitspresent in major surface? No Yes Yes No No No No X-ray diff.Direct-over-  100  100  250  120  100  90  80 peak FWHM subst. region(arcsec) Adjoin.-sub.  300  800  620  480  420  380  360 supra-regionMajor-surface Direct-over- 1 × 10⁷  1 × 10⁷  1 × 10⁷ 1 × 10⁷ 1 × 10⁷ 1 ×10⁷  1 × 10⁷  thread. disloc. subst. region dens. (cm⁻²) Adjoin.-sub. 3× 10⁷  8 × 10⁷  8 × 10⁷ 6 × 10⁷ 6 × 10⁷ 4 × 10⁷  4 × 10⁷  supra-regionCarrier concentration (cm⁻³) 5 × 10¹⁸ 5 × 10¹⁸  5 × 10¹⁸  5 × 10¹⁸  5 ×10¹⁸ 5 × 10¹⁸ 5 × 10¹⁸ Oxygen/cm³ 4 × 10¹⁸ 4 × 10¹⁸  2 × 10¹⁷ 3.2 ×10¹⁸  4.9 × 10¹⁸  2 × 10¹⁸ 3 × 10¹⁸ Silicon/cm³ 1 × 10¹⁸ 1 × 10¹⁸ 4.8 ×10¹⁸  1.8 × 10¹⁸   1 × 10¹⁷ 3 × 10¹⁸ 2 × 10¹⁸ Principal impurities O, SiO, Si O, Si O, Si O, Si O, Si O, Si Emb. 8 Emb. 9 Emb. 10 Emb. 11 Emb.12 Emb. 13 III-Nitride Substrate type GaN GaN GaN GaN GaN GaN crystalsubstrate Major-surface (12 30) (23 50) (20 21) (20 21) (22 41) (22 41)plane orient. Major-surface   5   5   5   5   5   5 roughness Ra (nm)Adjoining-surface   5   5   5   5   5   5 roughness Ra (nm) III-Nitridecrystal Crystal type GaN GaN GaN GaN GaN GaN Crystal growth method HVPEFlux HVPE HVPE HVPE HVPE Crystal growth 1050  870 1050 1050 1050 1050temperature (° C.) Major-surface (12 30) (23 50) (20 21) (20 21) (22 41)(22 41) plane orient. Pits present in major surface? Yes No No No YesYes X-ray diff. Direct-over-  280  230  120  90  220  200 peak FWHMsubst. region (arcsec) Adjoin.-sub.  660  490  380  360  580  480supra-region Major-surface Direct-over- 1 × 10⁷  1 × 10⁷ 1 × 10⁷  1 ×10⁷  3 × 10⁷  3 × 10⁷ thread. disloc. subst. region dens. (cm⁻²)Adjoin.-sub. 7 × 10⁷  4 × 10⁷ 4 × 10⁷  4 × 10⁷  7 × 10⁷  7 × 10⁷supra-region Carrier concentration (cm⁻³) 4 × 10¹⁸  3 × 10¹⁸ 1 × 10¹⁸ 1× 10¹⁸ 2 × 10¹⁸  2 × 10¹⁸ Oxygen/cm³ 2 × 10¹⁸ 2.5 × 10¹⁸  7 × 10¹⁷ 8 ×10¹⁷ 1 × 10¹⁸ 1.5 × 10¹⁸  Silicon/cm³ 2 × 10¹⁸  5 × 10¹⁷ 3 × 10¹⁷ 2 ×10¹⁷ 1 × 10¹⁸  5 × 10¹⁷ Principal impurities O, Si O, Si O, Si O, Si O,Si O, Si

As is evident from Table I, III-nitride crystal having a {h₀k₀i₀l₀}major surface was obtained by a III-nitride crystal manufacturing methodincluding: a step of slicing III-nitride bulk crystal into a pluralityof III-nitride crystal substrates having major surfaces of planeorientation {h₀k₀i₀l₀} other than {0001}, designated by choice; a stepof disposing the plurality of III-nitride crystal substrates adjoiningeach other sideways so that the major surfaces of the plurality ofIII-nitride crystal substrates parallel each other and so that the[0001] directions in the substrates be oriented in the same way; and astep of growing III-nitride crystal onto the major surfaces of theplurality of III-nitride crystal substrates.

Herein, as indicated by Embodiments 1 through 13, the fact that{h₀k₀i₀l₀} was—that the off-axis angle was—5° or less with respect toany crystallographically equivalent plane orientation selected from thegroup consisting of {1-10x} (wherein x is a whole number), {11-2y}(wherein y is a whole number), and {hk-(h+k)l} (wherein h, k and l arewhole numbers) meant that III-nitride crystal of superior crystallinity,having a {h₀k₀i₀l₀} major surface could be obtained. In particular, asindicated by Embodiment 1, the fact that {h₀k₀i₀l₀} was {1-100} meantthat III-nitride crystal of exceptionally superior crystallinity couldbe obtained.

Furthermore, as indicated by Embodiments 1 and 2, from the perspectiveof growing III-nitride crystal stably, it is preferable that theroughness average Ra of the surfaces along which the plurality ofIII-nitride crystal substrates adjoin be 50 nm or less, more preferably5 nm or less

Embodiment 14

Crystal of (1-102) orientation, manufactured in Embodiment 4, wasprocessed into a 0.4-mm thick, 2-inch diameter wafer, onto which,referring to FIG. 12, an LED structure 55 was formed by MOCVD tofabricate a light-emitting diode (LED) as a light-emitting semiconductordevice. In this instance, for growing the plurality of III-nitridecrystal layers that constituted the LED structure, trimethyl gallium(TMG), trimethyl indium (TMI), and/or trimethyl aluminum (TMA) wereutilized as the Group-III source material; ammonia was utilized as thenitrogen source material; monosilane was utilized as the n-type dopantsource material; and bis(cyclopentadienyl)magnesium (CP2Mg) was utilizedas the p-type dopant source material.

Specifically, as the plurality of III-nitride crystal layersconstituting the LED structure 55, an n-type GaN layer 51 of 2 μmthickness, a multiquantum well (MQW) light-emitting layer 52 of 88 nmthickness (seven In_(0.01)GaN barrier layers 52 b of 10 nm thickness andsix In_(0.14)GaN well layers 52 w of 3 nm thickness, arranged inalternating layers), a p-type Al_(0.18)GaN electron-blocking layer 53 of20 nm thickness, and a p-type GaN contact layer 54 of 50 nm thicknesswere grown, in that order, by MOCVD onto the major surface of a GaNcrystal substrate 20, with the (1-102) plane being the major surface.

As a p-side electrode 56, a transparent ohmic contact, constituted fromNi (5 nm)/Au (10 nm) and measuring 400 μm lengthwise×400 μm widthwise×15nm in thickness, was formed by vacuum evaporation deposition onto thep-type GaN contact layer 54. Then, as an n-side electrode 57, an ohmiccontact, constituted from Ti(20 nm)/Al(300 nm) and measuring 400 μmlengthwise×400 μm widthwise×320 nm in thickness, was formed by vacuumevaporation deposition onto the wafer major surface on the reverse sidefrom the MOCVD-growth side. The wafer was then segmented into chipsmeasuring 500 μm lengthwise×500 μm widthwise to complete the LEDs.

The thus obtained LEDs, with emission wavelength of 420 nm and, with anemission intensity of 4 mW to 5 mW when a 20 mA current was applied,demonstrating outstanding light output intensity, were ideally suited toLED applications.

Embodiment 15

Crystal of (20-21) orientation, manufactured in Embodiment 10, wasprocessed into a 0.4-mm thick, 2-inch diameter wafer, onto which,referring to FIG. 13, an LD structure 70 was formed by MOCVD tofabricate a laser diode (LD) as a light-emitting semiconductor device.In this instance, for growing the plurality of III-nitride crystallayers that constituted the LD structure, trimethyl gallium (TMG),trimethyl indium (TMI), and/or trimethyl aluminum (TMA) were utilized asthe Group-III source material; ammonia was utilized as the nitrogensource material; monosilane was utilized as the n-type dopant sourcematerial; and bis(cyclopentadienyl)magnesium (CP2Mg) was utilized as thep-type dopant source material.

Specifically, as the plurality of III-nitride crystal layersconstituting the LD structure 70, an n-type Al_(0.04)GaN layer 61 of 2μm thickness, an n-type GaN layer 62 of 50 nm thickness, an undopedIn_(0.03)GaN layer 63 of 65 nm thickness, a multiquantum well (MQW)light-emitting layer 64 (three In_(0.02)GaN barrier layers 64 b of 15 nmthickness and three In_(0.30)GaN well layers 64 w of 3 nm thickness,arranged in alternating layers), an undoped In_(0.03)GaN layer 65 of 50nm thickness, an undoped GaN layer 66 of 50 nm thickness, a p-typeAl_(0.18)GaN layer 67 of 20 nm thickness, a p-type Al_(0.06)GaN layer 68of 400 nm thickness, and a p-type GaN contact layer 69 of 50 nmthickness were grown, in that order, by MOCVD onto the major surface ofa GaN crystal substrate 20, with the (20-21) plane being the majorsurface.

As a p-side electrode 71, an ohmic contact, constituted from Ni (20nm)/Au (200 nm) and measuring 10 μm lengthwise×400 μm widthwise×220 nmin thickness, was formed by vacuum evaporation deposition onto thep-type GaN contact layer 69. Then, as an n-side electrode 72, an ohmiccontact, constituted from Ti (20 nm)/Al (300 nm) and measuring 400 μmlengthwise×400 μm widthwise×320 nm in thickness, was formed by vacuumevaporation deposition onto the wafer major surface on the reverse sidefrom the MOCVD-growth side. The wafer was then cleaved along the (1-120)plane into chips measuring 300 μm lengthwise×400 μm widthwise tocomplete the LDs.

The thus obtained LDs, demonstrating, with a lasing threshold current of420 mA and a lasing wavelength of 520 nm, outstanding device properties,were optimal as green LDs.

Embodiment 16

Crystal of (11-20) orientation, manufactured in Embodiment 3, wasprocessed into a 0.4-mm thick, 2-inch diameter wafer, onto which,referring to FIG. 14, a Schottky barrier diode structure was formed byMOCVD to fabricate a Schottky barrier diode (SBD) as a semiconductorelectronic device. In this instance, for growing the III-nitride crystallayer that constituted the SBD structure, trimethyl gallium (TMG), wasutilized as the Group-III source material, ammonia as the nitrogensource material, while monosilane was utilized as the n-type dopantsource material.

Specifically, as the III-nitride crystal layer constituting the SBDstructure, an n-type GaN layer 81 of 10 μm thickness was grown by MOCVDonto the major surface of a GaN crystal substrate 20, with the (11-20)plane being the major surface.

As a p-side electrode 82, a Schottky contact, constituted from Ni (20nm)/Au (200 nm) and measuring 400 μm lengthwise×400 μm widthwise×220 nmin thickness, was formed by vacuum evaporation deposition onto thesurface of the epitaxial layer that had been deposited by MOCVD. Inturn, as an n-side electrode 83, an ohmic contact, constituted from Ti(20 nm)/Al (300 nm) and measuring 400 μm lengthwise×400 μm widthwise×320nm in thickness, was formed by vacuum evaporation deposition onto thewafer major surface on the reverse side from the MOCVD-growth side. Thewafer was then segmented into chips measuring 5 mm lengthwise×5 mmwidthwise to complete fifty-two SBDs.

The blocking voltage of the obtained fifty-two SBDs was measured,whereupon the maximum was 1500 V and the minimum was 680 V, with theaverage being 1020 V. In addition, with a 50-amp on-resistance being aminimum 0.6 mΩ-cm² and a maximum 3 mΩ-cm² with the average being 0.8mΩ-cm², the devices had outstanding characteristics and thus wereideally suited as Schottky barrier diodes.

III-Nitride Bulk Crystal Preparation 2

AlN bulk crystal, as III-nitride bulk crystal utilized in a III-nitridecrystal manufacturing method involving the present invention, wasmanufactured by a method as below.

To begin with, AlN bulk crystal was deposited by sublimation growth ontothe (0001)-plane major surface of, as an undersubstrate, an SiCsubstrate of 51 mm diameter and 0.5 mm thickness. During the growth ofthe AlN bulk crystal, until it had grown to 0.5 mm thickness, 0.1 mass %CO₂ gas (Group-IV element-containing gas) was supplied, with the growthtemperature made 1700° C., to dope the crystal with carbon atoms asGroup IV dopants. Thereafter, while a growth temperature of 1800° C. wassustained, the supply of the Group-IV element-containing gas wasstopped, and an AlN bulk crystal of 5.5 mm thickness (including thejust-noted 0.5-mm thick portion doped with carbon atoms) was grown. Onthe (0001) face of the grown AlN bulk crystal, a plurality of hexagonalpyramidal pits defined by plural facets was formed.

Next, employing a mechanical polish, the SiC substrate was removed fromthe above-described AlN bulk crystal, yielding a 50-mm diameter, 3-mmthick AlN bulk crystal as III-nitride bulk crystal. At that time, theportion doped with Group IV dopants (carbon atoms) by supplying aGroup-IV element containing gas, and grown 5 mm thick, was eliminated.

Embodiment 17

To begin with, referring to FIG. 3A, the (0001) face and (000-1)face—the two major surfaces—of AlN bulk crystal (III-nitride bulkcrystal 1) were ground and polished to bring the roughness average Ra ofeither major surface to 5 nm.

Next, again referring to FIG. 3A: The AlN bulk crystal whose roughnessaverage Ra on either of its major surfaces had been made 5 nm was sawedalong a plurality of planes perpendicular to a <1-100> direction toslice off a plurality of AlN crystal substrates (III-nitride crystalsubstrates 10 p, 10 q) whose width S was 3 mm, length L was 20 to 50 mm,and thickness T was 1 mm, having {1-100} major surfaces. Subsequently,the not-ground and not-polished four sides of each sliced-off AlNcrystal substrate were ground and polished, to bring the roughnessaverage Ra of the four surfaces to 5 nm. A plurality of AlN crystalsubstrates whose roughness average Ra on the {1-100} major surfaces was5 nm was thus obtained. Among these AlN crystal substrates were AlNcrystal substrates whose major-surface plane orientation did notcoincide perfectly with {1-100}, but the plane orientation of the majorsurface of such AlN crystal substrates in all cases was misoriented by5° or less with respect to {1-100}.

Next, referring to FIG. 3B, these AlN crystal substrates were disposedadjoining each other sideways, in a manner such that the (1-100) majorsurfaces 10 pm, 10 qm of the plurality of AlN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the AlN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 3C, the roughness average Ra of the adjoining faces 10 pt, 10 qt ofthe plurality of AlN crystal substrates was 5 nm.

Next, with reference again to FIG. 3C, under a gaseous nitrogen ambientat 2200° C. AlN crystal (III-nitride crystal 20) was deposited bysublimation growth onto the (1-100) major surfaces 10 pm, 10 qm of thesituated plurality of AlN crystal substrates (III-nitride crystalsubstrates 10 p, 10 q) for 50 hours at a deposition rate of 100 μm/hr.

The obtained AlN crystal (III-nitride crystal 20), free of abnormalgrowth even in the adjoining-substrate supra-regions 20 t, had a (1-100)major surface 20 m. The crystallinity of the AlN crystal (III-nitridecrystal 20) was characterized by an x-ray diffraction rocking-curveanalysis of the (1-100) plane. With this AlN crystal, thedirect-over-substrate regions 20 s demonstrated diffraction peaksundivided in the tip, with the full-width at half-maximum being 30arcsec. Likewise, in the adjoining-substrate supra-regions 20 t as well,diffraction peaks without divisions in the tip were demonstrated, withthe full-width at half-maximum being 50 arcsec.

Furthermore, in the following manner the threading dislocation densityin the (1-100) major surface 20 m of the AlN crystal was determined.Namely, an AlN wafer (III-nitride crystal wafer 21), as represented inFIG. 3C, characterized by an area where the (1-100) plane was broadestwas sliced off. This AlN wafer (III-nitride crystal wafer 21) was heatedto 250° C., and the (1-100) major surface was etched by immersion of thewafer for one hour in a molten KOH—NaOH liquefied mixture (in massratio, KOH:NaOH=50:50). By observation of the (1-100) major surface ofthe etched AlN wafer (III-nitride crystal wafer 21) under an opticalmicroscope, the number of etch pits within a 100 μm×100 μm squaresurface was counted to calculate the etch-pit density (EPD) as themajor-surface threading dislocation density.

The threading dislocation density of the (1-100) major surface 20 m ofthe above-described AlN crystal was 1×10⁵ cm⁻² in thedirect-over-substrate region 20 s, and 2×10⁵ cm⁻² in theadjoining-substrate supra-regions 20 t. Meanwhile, the principalimpurities in the AlN crystal according to SIMS (secondary ion massspectrometry) were oxygen atoms and carbon atoms. The results aretabulated in Table II.

It should be understood that in Embodiment 17, the major-surface planeorientations of the plurality of AlN crystal substrates that were thesurfaces onto which the AlN crystal was grown were all (1-100), in thatalthough a few or more might have been (−1100), the crystallographicequivalent of (1-100), they would lead to the same results.

Embodiment 18

To begin with, referring to FIG. 3A, the (0001) face and (000-1)face—the two major surfaces—of AlN bulk crystal were ground and polishedto bring the roughness average Ra of either major surface to 50 nm.

Next, again referring to FIG. 3A: The AlN bulk crystal whose roughnessaverage Ra on either of its major surfaces had been made 50 nm was sawedalong a plurality of planes perpendicular to a <1-100> direction toslice off a plurality of AlN crystal substrates (III-nitride crystalsubstrates 10 p, 10 q) whose width S was 3 mm, length L was 20 to 50 mm,and thickness T was 1 mm, having {1-100} major surfaces. Subsequently,the not-ground and not-polished four sides of each sliced-off AlNcrystal substrate were ground and polished, to bring the roughnessaverage Ra of the four surfaces to 5 nm. A plurality of AlN crystalsubstrates whose roughness average Ra on the {1-100} major surfaces was5 nm was thus obtained. Among these AlN crystal substrates were AlNcrystal substrates whose major-surface plane orientation did notcoincide perfectly with {1-100}, but the plane orientation of the majorsurface of such AlN crystal substrates in all cases was misoriented by5° or less with respect to {1-100}.

Next, referring to FIG. 3B, these AlN crystal substrates were disposedadjoining each other sideways, in a manner such that the (1-100) majorsurfaces 10 pm, 10 qm of the plurality of AlN crystal substrates(III-nitride crystal substrates 10 p, 10 q) would be parallel to eachother, and such that the [0001] directions in the AlN crystal substrateswould be oriented in the same way. In this instance, referring also toFIG. 3C, the roughness average Ra of the adjoining faces 10 pt, 10 qt ofthe plurality of AlN crystal substrates was 50 nm.

Next, with reference again to FIG. 3C, under a gaseous nitrogen ambientat 2200° C. AlN crystal (III-nitride crystal 20) was deposited bysublimation growth onto the (1-100) major surfaces 10 pm, 10 qm of thesituated plurality of AlN crystal substrates (III-nitride crystalsubstrates 10 p, 10 q) for 50 hours at a deposition rate of 100 μm/hr.

The obtained AlN crystal (III-nitride crystal 20), free of abnormalgrowth even in the adjoining-substrate supra-regions 20 t, had a (1-100)major surface 20 m. In an x-ray diffraction rocking-curve analysis ofthe (1-100) plane of the AlN crystal, the direct-over-substrate regions20 s demonstrated diffraction peaks undivided in the tip, with thefull-width at half-maximum being 100 arcsec. Likewise, in theadjoining-substrate supra-regions 20 t as well, diffraction peakswithout divisions in the tip were demonstrated, with the full-width athalf-maximum being 150 arcsec. Furthermore, the threading dislocationdensity of the (1-100) major surface 20 m of the AlN crystal was 3×10⁵cm⁻² in the direct-over-substrate region 20 s, and 4×10⁵ cm⁻² in theadjoining-substrate supra-regions 20 t. Meanwhile, the principalimpurities in the AlN crystal were oxygen atoms and carbon atoms. Theresults are tabulated in Table II.

It should be understood that in Embodiment 18, the major-surface planeorientations of the plurality of AlN crystal substrates that were thesurfaces onto which the AlN crystal was grown were all (1-100), in thatalthough a few or more might have been (−1100), the crystallographicequivalent of (1-100), they would lead to the same results.

TABLE II Emb. 17 Emb. 18 III-Nitride Substrate type AlN AlN crystalMajor-surface plane orientation (1 100) (1 100) substrate Major-surface  5   5 roughness Ra (nm) Adjoining-surface   5   50 roughness Ra (nm)III-Nitride Crystal type AlN AlN crystal Crystal growth methodSublimation Sublimation Crystal growth  2200  2200 temperature (° C.)Major-surface plane orientation (1 100) (1 100) Pits present in majorsurface? No No X-ray Direct-over-   30  100 diffraction substrate peakFWHM region (arcsec) Adjoining-   50  150 substrate supra-regionMajor-surface Direct-over- 1 × 10⁵ 3 × 10⁵ threading substratedislocation region density Adjoining- 2 × 10⁵ 4 × 10⁵ (cm⁻²) substratesupra-region Carrier concentration (cm⁻³) — — Principal impurities O, CO, C

As is evident from Table II, III-nitride crystal having a {h₀k₀i₀l₀}major surface was obtained by a III-nitride crystal manufacturing methodincluding: a step of slicing III-nitride bulk crystal into a pluralityof III-nitride crystal substrates having major surfaces of planeorientation {h₀k₀i₀l₀} other than {0001}, designated by choice; a stepof disposing the substrates adjoining each other sideways so that themajor surfaces of the plurality of III-nitride crystal substratesparallel each other and so that the [0001] directions in the substratesbe oriented in the same way; and a step of growing III-nitride crystalonto the major surfaces of the plurality of III-nitride crystalsubstrates.

Herein, as is evident from a comparison between Embodiments 1 through 7in Table I and Embodiments 17 and 18 in Table II, it was found that inthe III-nitride crystal manufacturing methods, having the temperature atwhich the III-nitride crystal is grown be 2000° C. or greater remarkablyreduces the threading dislocation density in the major surface of theIII-nitride crystal.

The presently disclosed embodying modes and embodiment examples shouldin all respects be considered to be illustrative and not limiting. Thescope of the present invention is set forth not by the foregoingdescription but by the scope of the patent claims, and is intended toinclude meanings equivalent to the scope of the patent claims and allmodifications within the scope.

Group III-nitride crystal manufactured by a manufacturing methodinvolving the present invention is utilized in applications includingoptical elements (such as light-emitting diodes and laser diodes), insemiconductor electronic devices (such as rectifiers, bipolartransistors, field-effect transistors, or high electron mobilitytransistors (HEMTs)), semiconductor sensors (such as temperaturesensors, pressure sensors, radiation sensors, or visible-blindultraviolet detectors), surface acoustic wave devices (SAW devices),acceleration sensors, microelectromechanical system (MEMS) parts,piezoelectric oscillators, resonators, and piezoelectric actuators.

What is claimed is:
 1. A method of manufacturing III-nitride crystalhaving a major surface of plane orientation other than {0001},designated by choice, the III-nitride crystal manufacturing methodincluding: a step of slicing III-nitride bulk crystal through aplurality of planes defining a predetermined slice thickness in thedirection of the designated plane orientation, to produce a plurality ofIII-nitride crystal substrates having a major surface of the designatedplane orientation; a step of disposing the substrates adjoining eachother sideways in a manner such that the major surfaces of thesubstrates parallel each other and such that any difference in slicethickness between two adjoining III-nitride crystal substrates is notgreater than 0.1 mm; and a step of growing III-nitride crystal onto themajor surfaces of the substrates.
 2. A III-nitride crystal manufacturingmethod as set forth in claim 1, wherein the designated plane orientationis misoriented by an off angle of 5° or less with respect to anycrystallographically equivalent plane orientation selected from thegroup consisting of {1-10x} (wherein x is a whole number), {11-2y}(wherein y is a whole number), and {hk-(h+k)l} (wherein h, k and l arewhole numbers).
 3. A III-nitride crystal manufacturing method as setforth in claim 1, wherein the designated plane orientation ismisoriented by an off angle of 5° or less with respect to {1-100} planeorientations.
 4. A III-nitride crystal manufacturing method as set forthin claim 1, wherein the designated plane orientation is misoriented byan off angle of 5° or less with respect to any crystallographicallyequivalent plane orientation selected from the group consisting of{11-20}, {1-10±2}, {11-2±2}, {20-2±1} and {22-4±1}.
 5. A III-nitridecrystal manufacturing method as set forth in claim 1, wherein theroughness average Ra of the faces along which the substrates adjoin eachother is 50 nm or less.
 6. A III-nitride crystal manufacturing method asset forth in claim 1, further comprising a step of grinding/polishingthe plurality of III-nitride crystal substrates such that the surfaceroughness of the substrate major surfaces is not greater than 50 nm.